Device for forming a sand body and method for the application thereof

ABSTRACT

A device for forming a siltation construction comprising a substantially rectangular cloth ( 1 ) of water-permeable material, which is anchored on all sides to a water bed by anchoring means. Floating elements ( 10 ) are arranged on cloth at a distance from one side ( 4 ) thereof and along the other sides ( 3 ) are formed pouches ( 1 ) open toward the center of the cloth.

BACKGROUND OF THE INVENTION

1. Technical Field of the Invention

The invention relates to a device for forming a siltation constructioncomprising a substantially rectangular cloth of water-permeablematerial. Such a cloth is anchored on all sides with anchoring means toa water bed and floating means are arranged on the cloth which pull thecloth upward relative to the bed.

2. Description of the Prior Art

Such a device is known from the Netherlands patent application 9101525.

SUMMARY OF THE INVENTION

The invention has for its object to further improve a device as knownfrom the prior art such that in more efficient manner a siltationconstruction can therewith be formed and preserved in durable manner.

This object is achieved with the device according to the invention inthat the floating means are arranged at a distance from one side of thecloth and along the other sides are formed pouches open toward thecentre of the cloth. The cloth is anchored to the water bed by theanchoring means with the open side of the pouches facing upward. A waterflow filled with sediment which moves along the cloth will also flowinto the open pouches and come to rest there locally. The sedimenthereby settles in and around the pouches. Within a very short time thesides of the cloth where the pouches are situated are thus incorporatedin the water bed in well closed-in manner.

The side of the cloth not provided with pouches is anchored at somedistance. The floating means arranged close to this side hold up thisside of the cloth, hereby water charged with sand and optionally othersediment can flow into the space beneath the cloth. Because the flowbecomes calmer here, the sediment will settle and the desired siltationconstruction will thus be formed.

Because the floating means are arranged on the underside of the cloth inthe situation of use, they are situated in a relatively calmenvironment, so that they do not suffer damage. The upper side of thecloth herein remains smooth, whereby a uniform flow occurs over thecloth.

An advantageous method of fixing the floating means is to accommodatethem in a tunnel which is sewn onto the cloth parallel to the one sideof the cloth not provided with the pouches. The floating means can thenbe pushed into and later optionally also pushed out of this tunnel.

A further very favourable development of the invention is obtained by aclosing cloth connected to the cloth at a distance parallel to the oneside thereof and having a dimension transversely of the connecting sidelarger than this distance. After sufficient sediment has been depositedbeneath the cloth, or optionally in the interim, this closing cloth canbe laid over the open side of the cloth and anchored to the bed. Theformed sand body is hereby protected and enclosed on all sides by thecloth and the closing cloth.

Preferably applied herein along the side of the closing cloth oppositethe connecting side are pouches which are open toward the connectingside. In the situation where the closing cloth is laid over the opening,these pouches will also become filled with sediment and be incorporatedin the bed, whereby here also a good closing-in is effected. Laterwashing away of the sand body is hereby prevented to a large degree.

The device can further comprise fixing means for fastening the closingcloth in rolled-up position. As long as siltation still takes place andthe one side of the cloth therefore remains open, the closing cloth canbe fastened with these fixing means.

Another favourable embodiment is obtained when additional floating meansare arranged along the side of the closing cloth opposite the connectingside. The closing cloth can hereby stand vertically upward in thesiltation phase. On the one hand the free side of the cloth fixed to thebed is hereby held up and on the other hand the upright closing clothforms a flow barrier which contributes toward calming of the water flowand thereby toward settling of the sediment in this water.

The floating means are accommodated in favourable manner in a tunnelwhich is sewn onto the free end of the closing cloth. Once the siltationphase has ended, the floating means can then be removed simply from thetunnel by a diver, whereafter the closing cloth can be secured.

It is noted that if the closing cloth is provided along the free edgewith the above described pouches open on one side, these pouches will beopen downward in the vertically upright position of the closing cloth,so that in this situation no sediment can accumulate in these pouches.Only when the closing cloth has been folded over the opening and thepouches therefore assume a substantially lying position will theyquickly be filled with sediment and provide the desired closing-in.

The invention likewise relates to and provides a method for forming asand body on a bed of a body of water in which a sediment-charged flowoccurs. In this method a plurality of the above described devicesaccording to the invention are used. These are anchored mutuallyadjacently to the bed. One or more continuous sand bodies can thus beformed in durable manner in a flow charged with sediment.

The method is particularly suitable for preventing or reversing erosionin sea or river flows at coasts and river banks.

When the sediment-charged flow arrives via the open side under the clothwhich is further held up by floating means, the speed of the flowdecreases, whereby under, on and around the cloth sedimentation willoccur continuously. The water, now charged to a lesser degree withsediment, will escape through the meshes of the cloth.

BRIEF DESCRIPTION OF THE DRAWING FIGURES

The invention will be further elucidated in the following descriptionwith reference to the annexed figures.

FIG. 1 shows a number of devices according to the invention for forminga sand body in the siltation phase.

FIG. 2 shows one of the devices according to the invention shown in FIG.1 after siltation is completed.

FIGS. 3 and 4 elucidate schematically the water flow during use of themethod according to the invention.

DETAILED DESCRIPTION OF THE DRAWING AND PREFERRED EMBODIMENTS

Designated with 1 in FIG. 1 is a device according to the invention. Thissubstantially comprises a rectangular cloth 2 of material which iswater-permeable but the meshes of which are of dimensions such thatsediment, in particular sand, cannot easily flow out through thesemeshes.

Along three sides 3, referred to hereinbelow as fastening edges, thecloth is secured to the bed of a body of water with anchoring means. Thefourth edge 4, referred to hereinbelow as free edge, is also anchored tothis bed but at some distance, so that it can remain clear of the bed.

The anchoring means are formed in this embodiment by anchors 6 which canbe placed in the bed in random suitable manner. This preferably takesplace by means of injection, wherein water is fed through a central tubeof anchor 6 which carries away soil from beneath the anchor and thuscreates space to allow anchor 6 to sink. When anchor 6 is arranged atthe correct depth, the water supply is discontinued.

Arranged at the top of the tube of anchor 6 is a chain 7, on the end ofwhich is mounted a floater 8.

All anchoring means for one cloth 2 can be arranged in advance in thebed. This can be carried out in simple manner by divers.

When the anchors are arranged, the cloth 2 is taken for instance by boatto a position above the chosen location and fixed to the anchoringmeans.

It is noted that the cloth is very light, for instance only 0.2 kg/m²,while cloth 2 itself measures for instance 25 m×25 m, so that it can behandled easily by a few people.

The lowered cloth is fixed to the chains 7 of the anchoring means. Thefloating bodies 8 herein serve of course to enable locating of the endsof chains 7.

As noted, the free edge 4 of cloth 2 is fastened at a greater distance,in that chains 9 have a greater length than chains 7. On the undersideof cloth 2 close to free edge 4 a floating body 10 is accommodated in atunnel formed for this purpose on the underside of cloth 2. This floater10 ensures that free edge 4 is held up at a distance from the bed. Watercharged with sediment, particularly sand, can flow through below freeedge 4 in the direction of arrow 16 beneath the cloth 2, where the flowwill become considerably calmer and the sediment will settle. The waterescapes through cloth 2.

Formed along the fastening edges 3 of cloth 2 are pouches 11 which areopen toward the centre of the cloth. These pouches 11 will likewise befilled with sediment by water flows indicated with arrows 12 wherebyfastening edges 3 are thus made heavier and close well against the bed.Through siltation all around the fastening edge 3 will gradually beincorporated into the bed.

In the shown preferred embodiment a closing cloth 13 is fixed to thecloth 2 at a distance parallel to free edge 4. This closing cloth 13 isa rectangular piece of cloth which in this embodiment has on its freeupper edge a tunnel 15 in which a floater 14 is received. Due to thebuoyancy of this floater 14 the cloth 13 will assume the uprightposition shown in FIG. 1. The upright closing cloth 13 reduces the flowover the surface of cloth 2, which contributes toward settling of thesediment taken up in the flowing water.

FIG. 3 shows more particularly a side view of an array of devices 1according to the invention which are arranged in the vicinity of acoastline. It is known that through the surging movement of waves 25 thebed 27 can be considerably washed away and the coastline can thus beeroded significantly in a short time. In order to prevent this an arrayof devices 1 as shown in FIG. 1 is arranged mutually adjacently andsubstantially parallel to the coastline, in order to form a naturalsandbank in durable manner with the sedimentation enhanced by the clothwhich prevents further erosion of the coast.

Sediment from the bed 27 is carried along in large quantities by thebreaking waves 25 in the return flow 26. This return flow 26 is capturedby the free opening 28 of the mutually adjacent devices 1. The sedimenttaken up in the flow settles beneath the cloth of device 1 whereby thedesired, naturally formed, durable sandbank is formed. After the spaceunder the cloth is completely filled with sediment, the closing cloth 29is closed over free opening 28, whereafter further siltation 29 as shownin FIG. 4 will occur, resulting in a durable sandbank in a naturalstreamlined shape for protection of the coastline. The strength of thesurging movement is reduced by the thus formed sandbank and further bederosion is prevented, while siltation between the sandbank and the coastwill be enhanced.

FIG. 2 shows in more detail a device 1 according to the invention,wherein closing cloth 13 is folded over the opening and thus covers it.

When sufficient sediment has thus deposited under cloth 2, a diver 21removes the floater 14 from the tunnel 15 on the end of closing cloth13. Closing cloth 13 is subsequently folded over the opening in themanner shown in FIG. 2 and fastened using anchoring means which are notshown in detail here.

As shown in FIG. 2, the free edge of closing cloth 13 is provided withpouches 18 which are gradually filled with sediment in the same manneras pouches 11 and thus hold the free edge of closing cloth 13 in firmcontact with the bed and are subsequently entirely incorporated therein.In the situation shown in FIG. 2 the formed siltation construction isprotected against damage by unexpected influences, such as extra-strongsurge and eroding currents.

What is claimed is:
 1. A device for forming a siltation constructioncomprising a substantially rectangular cloth of water-permeablematerial, anchoring means for anchoring the cloth on all sides to awater bed, wherein floating means are arranged on the cloth at adistance from one side of said cloth and wherein along the other sidesof said cloth are formed pouches having openings facing toward thecenter of the cloth.
 2. The device as claimed in claim 1, wherein thefloating means are arranged on a surface of the cloth opposite thesurface of the cloth on which the pouches are formed.
 3. The device asclaimed in claim 2, wherein the floating means are accommodated in atunnel which is sewn onto the cloth and parallel to the one side.
 4. Thedevice as claimed in claim 1, further comprising a closing clothconnected at a distance to the cloth parallel to the one side of thecloth and having a dimension extending transversely of the connectingside, wherein said dimension is longer than said distance.
 5. The deviceas claimed in claim 4, further including additional pouches on saidclosing cloth wherein said additional pouches are formed along the sideof the closing cloth lying opposite the connecting side.
 6. The deviceas claimed in claim 4, wherein fixing means are provided for fasteningthe closing cloth in rolled-up position.
 7. The device as claimed inclaim 4, wherein additional floating means are arranged along the sideof the closing cloth opposite the connecting side.
 8. The device asclaimed in claim 7, wherein the additional floating means areaccommodated in a tunnel sewn onto the cloth.
 9. A method for forming asand body on a bed of a body of water in which a sediment-charged flowoccurs, utilizing a plurality of devices, each of said devicesincluding: a substantially rectangular cloth of water-permeablematerial; anchoring means for anchoring the cloth on all sides to awater bed; and, floating means being arranged on said cloth at adistance from one side thereof and wherein along remaining sides of saidcloth, pouches are formed open toward a central point of said cloth,comprising the step of: anchoring said plurality of devices mutuallyadjacently to the bed.
 10. The method as claimed in claim 9, whereineach said plurality of devices is provided with a closing cloth, andfurther including after forming the sand body, folding said closingcloth of each of said plurality of devices over said one side andanchoring each said closing cloth to the bed.